Human respiratory syncytial virus (RSV) and parainfluenza virus (PIV), members of the paramyxovirus family, are major pathogens responsible for severe respiratory disease in infants and young children (Glezen et al., 1981; Chanock et al., 1992; Martin et al., 1978). Two groups of RSV, group A (RSV-A) and group B (RSV-B), circulate simultaneously during yearly winter epidemics, although a predominance of Group A infections is usually noted (McConnochie et al., 1990; Stark et al., 1991). PIV type 3 (PIV-3) is a common cause of bronchiolitis, pneumonia and croup. Together, RSV and PIV-3 account for up to 30% of all hospitalizations of infants and young children for respiratory tract disease (Crowe, 1995). PIV types 1 and 2 (PIV-1 and PIV-2) are also common causes of croup. RSV has also been reported to cause significant morbidity in immunocompromised individuals and the elderly. Sixty-five million RSV infections occur globally every year, resulting in 160,000 deaths (Robbins and Freeman, 1988). In the United States alone, 100,000 children are hospitalized annually with severe cases of pneumonia and bronchiolitis resulting from an RSV infection (Glezen et al., 1986; Katz, 1985). Inpatient and ambulatory care for children with RSV infections in the U.S. was estimated in 1992 to cost in excess of $340 million per year (Wertz and Sullender, 1992). The World Health Organization (WHO) (Crowe, 1995) and the National Institute of Allergy and Infectious Disease (NIAID) vaccine advisory committees have ranked RSV second only to HIV for vaccine development, while the preparation of an efficacious PIV (e.g., PIV type 3) vaccine is ranked in the top ten vaccines considered a priority for vaccine development.
Thus, an urgent need remains for the ability to engineer a safe and effective RSV and/or PIV vaccine that is able to prevent serious respiratory diseases in infants, young children, elderly and the immunocompromised. The use of live attenuated RSV and/or PIV to control respiratory disease is one of the more promising approaches. A number of live attenuated RSV strains have been developed and tested in RSV-seronegative children during the past twenty years. The most pursued approaches for live attenuation of RSV have been cold-passaged (cp) RSV, temperature-sensitive (ts) RSV mutants and cold-passage temperature sensitive (cpts) RSV mutants (Kneyber and Kimpen, 2002). RSV mutants such as cpts-248, cpts-248/404, cpts-530 and PIV-3 mutant cp-45 are currently being evaluated in laboratories and clinical trials.
In addition to a need for the identification and development of an efficacious live attenuated RSV, PIV or RSV/PIV combination immunogenic compositions, there is currently a need for methods of producing storage stable RSV and/or PIV compositions and immunogenic compositions thereof. For example, RSV is a heat labile virus, which is inactivated in less than three months during storage at −65° C. to −86° C. (Hambling, 1964; Wulff et al., 1964; Gupta et al., 1996). It is therefore highly desirable to identify methods for producing RSV, PIV or RSV/PIV immunogenic compositions which are storage stable.
Furthermore, enhancing the storage stability of other viral immunogenic compositions has long been recognized as an important goal for improving the impact of vaccines on world health (Melnick and Wallis, 1963; Rasmussen et al., 1973; Ayra, 2001; Hilleman, 1989; Lemon and Milstein, 1994). There is therefore a need in the art of virus formulation and process development for methods of producing storage stable virus compositions such as herpes simplex virus, cytomegalovirus, Epstein-Barr virus, Varicella-Zoster virus, mumps virus, measles virus, influenza virus, poliovirus, rhinovirus, adenovirus, hepatitis A virus, hepatitis B virus, hepatitis C virus, Norwalk virus, togavirus, alphavirus, rubella virus, rabies virus, Marburg virus, Ebola virus, papilloma virus, polyoma virus, metapneumovirus, coronavirus, vesicular stomatitis virus, Venezuelan equine encephalitis virus and the like.